Ceramic substrates are employed in electronic packaging applications. Multilayer substrates that are interspersed with metallic connects are used to support and wire several electronic or opto-electronic components in order to construct a functional module. The state-of-the-art in multilayer ceramic substrate technology has been represented by the IBM multilayer ceramic substrate as described in Blodgett, A.J., et al, IBM J. Res. Develop. 26, 1, pp. 30-36 (1982). The IBM multilayer ceramic substrate is prepared by laminating alumina ceramic tapes and screen printed metal pastes. This "green" structure is then co-fired at approximately 1700.degree. C. in a reducing hydrogen containing atmosphere. The substrate shrinks in the x, y, and z directions during sintering, approximately 17% in each direction, and such shrinkage in the x-y plane may cause interface defects and delamination.
The above technology has evolved so that glass or glass ceramic dielectrics are being used in place of alumina to reduce the sintering temperature to less than 1000.degree. C. so that copper can be used for metallization. Furthermore, attempts have been made to restrict x-y shrinkage by attaching the dielectric tapes to a monolithic substrate before sintering. In general, this restricts the ability to co-fire multilayer assemblies.
The present invention essentially eliminates x-y plane shrinkage and the associated delamination without requiring attachment to a monolithic substrate.